"make known by open declaration, publish, announce" (a decree, news, etc.), 1520s, from Latin promulgatus, past participle of promulgare "make publicly known, propose openly, publish," probably from pro "forth" (see pro-) + mulgere "to milk" (see milk (n.)), used metaphorically for "cause to emerge." In that case the word is "a picturesque farmers' term used originally of squeezing the milk from the udder" [L.R. Palmer, "The Latin Language"]. Related: Promulgated; promulgating. The earlier verb in English was promulge (late 15c.).